Radio communication apparatus and radio communication method

ABSTRACT

Provided is a radio communication device which can make Acknowledgement (ACK) reception quality and Negative Acknowledgement (NACK) reception quality to be equal to each other. The device includes: a scrambling unit ( 214 ) which multiplies a response signal after modulated, by a scrambling code “1” or “e −j(π/2) ” so as to rotate a constellation for each of response signals on a cyclic shift axis; a spread unit ( 215 ) which performs a primary spread of the response signal by using a Zero Auto Correlation (ZAC) sequence set by a control unit ( 209 ); and a spread unit ( 218 ) which performs a secondary spread of the response signal after subjected to the primary spread, by using a block-wise spread code sequence set by the control unit ( 209 ).

TECHNICAL FIELD

The present invention relates to a radio communication apparatus andconstellation control method.

BACKGROUND ART

In mobile communication, Automatic Repeat Request (ARQ) is applied todownlink data from a radio communication base station apparatus(hereinafter abbreviated to “base station”) to radio communicationmobile station apparatuses (hereinafter abbreviated to “mobilestations”). That is, mobile stations feed back response signalsrepresenting error detection results of downlink data, to the basestation. Mobile stations perform a Cyclic Redundancy Check (CRC) ofdownlink data, and, if CRC=OK is found (i.e., if no error is found),feed back an Acknowledgement (ACK), and, if CRC=NG is found (i.e., iferror is found), feed back a NACK (Negative ACKnowledgement), as aresponse signal to the base station. These response signals aretransmitted to the base station using uplink control channels such as aPhysical Uplink Control Channel (PUCCH).

Also, the base station transmits control information for carryingresource allocation results of downlink data, to mobile stations. Thiscontrol information is transmitted to the mobile stations using downlinkcontrol channels such as L1/L2 Control Channels (L1/L2 CCHs). Each L1/L2CCH occupies one or a plurality of Control Channel Elements (CCEs) basedon the coding rate of control information. For example, when a L1/L2 CCHfor carrying control information coded by a rate of ⅔ occupies one CCE,a L1/L2 CCH for carrying control information coded by a rate of ⅓occupies two CCEs, a L1/L2 CCH for carrying control information coded bya rate of ⅙ occupies four CCEs and a L1/L2 CCH for carrying controlinformation coded by a rate of 1/12 occupies eight CCEs. Also, when oneL1/L2 occupies a plurality of CCEs, the CCEs occupied by the L1/L2 CCHare consecutive. The base station generates a L1/L2 CCH on a per mobilestation basis, assigns CCEs to be occupied by L1/L2 CCH's based on thenumber of CCEs required by control information, and maps the controlinformation on physical resources corresponding to the assigned CCEs andtransmits the control information.

Also, studies are underway to map between CCEs and PUCCHs on aone-to-one basis, to use downlink communication resources efficientlywithout signaling from a base station to mobile stations to report thePUCCHs to be used for transmission of response signals, (see Non-PatentDocument 1). According to this mapping, each mobile station can decidethe PUCCH to use to transmit response signals from the mobile station,from the CCEs corresponding to physical resources on which controlinformation for the mobile station is mapped. Therefore, each mobilestation maps a response signal from the mobile station on a physicalresource, based on the CCE corresponding to a physical resource on whichcontrol information directed to the mobile station is mapped. Forexample, when a CCE corresponding to a physical resource on whichcontrol information directed to the mobile station is mapped, is CCE #0,the mobile station decides PUCCH #0 associated with CCE #0 as the PUCCHfor the mobile station. Also, for example, when CCEs corresponding tophysical resources on which control information directed to the mobilestation is mapped are CCE #0 to CCE #3, the mobile station decides PUCCH#0 associated with CCE #0, which is the smallest number in CCE #0 toCCE#3, as the PUCCH for the mobile station, and, when CCEs correspondingto physical resources on which control information directed to themobile station is mapped are CCE #4 to CCE #7, the mobile stationdecides PUCCH #4 associated with CCE #4, which is the smallest number inCCE #4 to CCE#7, as the PUCCH for the mobile station.

Also, as shown in FIG. 1, studies are underway to performcode-multiplexing by spreading a plurality of response signals from aplurality of mobile stations using Zero Auto Correlation (ZAC) sequencesand Walsh sequences (see Non-Patent Document 1). In FIG. 1, [W₀, W₁, W₂,W₃] represents a Walsh sequence with a sequence length of 4. As shown inFIG. 1, in a mobile station, first, a response signal of ACK or NACK issubject to first spreading to one symbol by a ZAC sequence (with asequence length of 12) in the frequency domain. Next, the responsesignal subjected to first spreading is subject to an IFFT (Inverse FastFourier Transform) in association with W_(o) to W₃. The response signalspread in the frequency domain by a ZAC sequence with a sequence lengthof 12 is transformed to a ZAC sequence with a sequence length of 12 bythis IFFT in the time domain. Then, the signal subjected to the IFFT issubject to second spreading using a Walsh sequence (with a sequencelength of 4). That is, one response signal is allocated to each of fourSC-FDMA (Single Carrier-Frequency Division Multiple Access) symbols S₀to S₃. Similarly, response signals of other mobile stations are spreadusing ZAC sequences and Walsh sequences. Here, different mobile stationsuse ZAC sequences of different cyclic shift values in the time domain(i.e., in the cyclic shift axis) or different Walsh sequences. Here, thesequence length of ZAC sequences in the time domain is 12, so that it ispossible to use twelve ZAC sequences of cyclic shift values “0” to “11,”generated from the same ZAC sequence. Also, the sequence length of Walshsequences is 4, so that it is possible to use four different Walshsequences. Therefore, in an ideal communication environment, it ispossible to code-multiplex maximum forty-eight (12×4) response signalsfrom mobile stations.

Also, as shown in FIG. 1, studies are underway for code-multiplexing aplurality of reference signals (e.g., pilot signals) from a plurality ofmobile stations (see Non-Patent Document 2). As shown in FIG. 1, in thecase of generating three symbols of reference signals R₀, R₁ and R₂,similar to the case of response signals, first, the reference signalsare subject to first spreading in the frequency domain by a sequencehaving characteristics of a ZAC sequence (with a sequence length of 12)in the time domain. Next, the reference signals subjected to firstspreading are subject to an IFFT in association with orthogonalsequences with a sequence length of 3, [F₀, F₁, F₂], such as a Fouriersequence. The reference signals spread in the frequency domain areconverted by this IFFT to ZAC sequences with a sequence length of 12 inthe time domain. Further, these signals subjected to IFFT are subject tosecond spreading using orthogonal sequences [F₀, F₁, F₂]. That is, onereference signal is allocated to three SC-FDMA symbols R₀, R₁ and R₂.Similarly, other mobile stations allocate one reference signal to threesymbols R₀, R₁ and R₂. Here, different mobile stations use ZAC sequencesof different cyclic shift values in the time domain or differentorthogonal sequences. Here, the sequence length of ZAC sequences in thetime domain is 12, so that it is possible to use twelve ZAC sequences ofcyclic shift values “0” to “11,” generated from the same ZAC sequence.Also, the sequence length of an orthogonal sequence is 3, so that it ispossible to use three different orthogonal sequences. Therefore, in anideal communication environment, it is possible to code-multiplexmaximum thirty-six (12×3) reference signals from mobile stations.

As shown in FIG. 1, seven symbols of S₀, S₁, R₀, R₁, R₂, S₂ and S₃ formone symbol.

Here, there is substantially no cross correlation between ZAC sequencesof different cyclic shift values generated from the same ZAC sequence.Therefore, in an ideal communication environment, a plurality ofresponse signals subjected to spreading and code-multiplexing by ZACsequences of different cyclic shift values (0 to 11), can be separatedin the time domain substantially without inter-code interference, bycorrelation processing in the base station.

However, due to an influence of, for example, transmission timingdifference in mobile stations and multipath delayed waves, a pluralityof response signals from a plurality of mobile stations do not alwaysarrive at a base station at the same time. For example, if thetransmission timing of a response signal spread by the ZAC sequence ofcyclic shift value “0” is delayed from the correct transmission timing,the correlation peak of the ZAC sequence of cyclic shift value “0” mayappear in the detection window for the ZAC sequence of cyclic shiftvalue “1.”

Further, if a response signal spread by the ZAC sequence of cyclic shiftvalue “0” has a delay wave, an interference leakage due to the delayedwave may appear in the detection window for the ZAC sequence of cyclicshift value “1.” That is, in these cases, the ZAC sequence of cyclicshift value “1” is interfered with by the ZAC sequence of cyclic shiftvalue “0.” On the other hand, if the transmission timing of a responsesignal spread by the ZAC sequence of cyclic shift value “1” is earlierthan the correct transmission timing, the correlation peak of the ZACsequence of cyclic shift value “1” may appear in the detection windowfor the ZAC sequence of cyclic shift value “0.” That is, in this case,the ZAC sequence of cyclic shift value “0” is interfered with by the ZACsequence of cyclic shift value “1.” Therefore, in these cases, theseparation performance degrades between a response signal spread by theZAC sequence of cyclic shift value “0” and a response signal spread bythe ZAC sequence of cyclic shift value “1.” That is, if ZAC sequences ofadjacent cyclic shift values are used, the separation performance ofresponse signals may degrade.

Therefore, up till now, if a plurality of response signals arecode-multiplexed by spreading using ZAC sequences, a sufficient cyclicshift value difference (i.e., cyclic shift interval) is provided betweenthe ZAC sequences, to an extent that does not cause inter-codeinterference between the ZAC sequences. For example, when the differencebetween cyclic shift values of ZAC sequences is 2, only six ZACsequences of cyclic shift values “0,” “2,” “4,” “6,” “8” and “10” orcyclic shift values “1,” “3,” “5,” “7,” “9” and “11” amongst twelve ZACsequences of cyclic shift values “0” to “12,” are used for firstspreading of response signals. Therefore, if a Walsh sequence with asequence length of 4 is used for second spreading of response signals,it is possible to code-multiplex maximum twenty-four (6×4) responsesignals from mobile stations.

However, as shown in FIG. 1, the sequence length of an orthogonalsequence used to spread reference signals is 3, and therefore only threedifferent orthogonal sequences can be used to spread reference signals.Consequently, when a plurality of response signals are separated usingthe reference signals shown in FIG. 1, only maximum eighteen (6×3)response signals from mobile stations can be code-multiplexed. That is,three Walsh sequences are required amongst four Walsh sequences with asequence length of 4, and therefore one Walsh sequence is not used.

Also, the 1 SC-FDMA symbol shown in FIG. 1 may be referred to as “1 LB(Long Block).” Therefore, a spreading code sequence that is used inspreading in symbol units or LB units, is referred to as a “block-wisespreading code sequence.”

Also, studies are underway to define eighteen PUCCHs as shown in FIG. 2.Normally, the orthogonality of response signals does not collapsebetween mobile stations using different block-wise spreading codesequences, as long as the mobile stations do not move fast. But,especially if there is a large difference of received power betweenresponse signals from a plurality of mobile stations at a base station,one response signal may be interfered with by another response signalbetween mobile stations using the same block-wise spreading codesequence. For example, in FIG. 2, a response signal using PUCCH #1(cyclic shift value=2) may be interfered with by a response signal usingPUCCH #0 (cyclic shift value=0).

Also, studies are underway to use the constellation shown in FIG. 3 whenBPSK is used as the modulation scheme for response signals, and theconstellation shown in FIG. 4 when QPSK is used as the modulation schemefor response signals (see Non-Patent Document 3).

-   Non-Patent Document 1: NTT DoCoMo, Fujitsu, Mitsubishi Electric,    “Implicit Resource Allocation of ACK/NACK Signal in E-UTRA Uplink,”    3GPP TSG RAN WG1 Meeting #49, R1-072439, Kobe, Japan, May 7-11,    2007.-   Non-Patent Document 2: Nokia Siemens Networks, Nokia, “Multiplexing    capability of CQIs and ACK/NACKs form different UEs,” 3GPP TSG RAN    WG1 Meeting #49, R1-072315, Kobe, Japan, May 7-11, 2007.-   Non-Patent Document 3: 3GPP; TSG RAN, Evolved Universal Terrestrial    Radio Access (E-UTRA); “Physical Channels and Modulation (Release    8),” 3GPP TS 36.211 V8.0.0, September 2007.

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

An example case will be described below where the constellation shown inFIG. 3 is used to modulate a response signal. Also, an example case willbe described below where one mobile station #1 transmits a responsesignal using PUCCH #1 (in FIG. 2) and another mobile station #2transmits a response signal using PUCCH #0 (in FIG. 2). In this case,the base station performs the above-described correlation processing todistinguish between the response signal from mobile station #1 and theresponse signal from mobile station #2. At this time, components of theresponse signal from mobile station #2 may leak in the correlationoutput to receive the response signal of mobile station #1, andinterfere with the response signal of mobile station #1.

Then, when mobile station #1 and mobile station #2 both transmit an ACKand the base station receives the response signal from mobile station#1, interference given from the response signal of mobile station #2 tothe response signal of mobile station #1 is as follows.

That is, when the ACK and reference signal transmitted from mobilestation #1 are received by the base station via a channel, in the basestation, a response signal represented by (−1−j) h1/√2 and referencesignal represented by (1+j) h1/√2 are found as a correlation output ofmobile station #1. Here, h1 is an effective channel in a case where thesignals from mobile station #1 pass a channel between mobile station #1and the base station, and are found, as a correlation output, in thedetection window for mobile station #1 in the base station.

Also, when the ACK and reference signal transmitted from mobile station#2 are received by the base station via a channel, in the base station,a component represented by (−1−j) h2/√2 is found as interference to theresponse signal of mobile station #1 and a component represented by(1+j) h2/√2 is found as interference to the reference signal of mobilestation #1 in the correlation output of mobile station #1. Here, h2 isan effective channel in a case where the signals from mobile station #2passes a channel between mobile station #2 and the base station, andleak, as the correlation output, in the detection window for mobilestation #1 in the base station.

When there is little delay on a channel and no transmission timingdifference at a mobile station, such a leak does not occur. But,depending on conditions, h2 may be non-negligibly high for h1.Therefore, when an ACK from mobile station #1 and ACK from mobilestation #2 are code-multiplexed, in the base station, a response signalrepresented by (−1−j)(h1+h2)/√2 and reference signal represented by(1+j)(h1+h2)/√2 are found in the correlation output of mobile station#1.

Therefore, the interference component given from the ACK of mobilestation #2 to the ACK of mobile station #1 (i.e., the Euclidean distancefrom (−1−j)/√2) by the synchronous detection in the base station, isrepresented by equation 1. That is, when both mobile station #1 andmobile station #2 transmit an ACK, there is no inter-code interferencebetween the ACK of mobile station #1 and the ACK of mobile station #2.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 1} \right)\mspace{610mu}} & \; \\{{{\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( {{- 1} - \frac{{- h_{1}} - h_{2}}{h_{1} + h_{2}}} \right)} = 0}\mspace{14mu}} & \lbrack 1\rbrack\end{matrix}$

Also, when mobile station #1 transmits a NACK, mobile station #2transmits an ACK and the base station receives the response signal frommobile station #1, interference from the response signal of mobilestation #2 to the response signal #1 is as follows.

That is, when the NACK and reference signal transmitted from mobilestation #1 are received by the base station via a channel, in the basestation, a response signal represented by (1+j)h1/√2 and referencesignal represented by (1+j)h1/√2 are found as a correlation output ofmobile station #1.

Also, when the ACK and reference signal transmitted from mobile station#2 are received by the base station via a channel, in the base station,a component represented by (−1−j)h2/√2 is found as interference to theresponse signal of mobile station #1 and a component represented by(1+j)h2/√2 is found as interference to the reference signal of mobilestation #1 in the correlation output of mobile station #1.

Therefore, when the NACK from mobile station #1 and the ACK from mobilestation #2 are code-multiplexed, in the base station, a response signalrepresented by (1+j)(h1−h2)/√2 and reference signal represented by(1+j)(h1+h2)/√2 are found in the correlation output of mobile station#1.

Therefore, the interference component given from the ACK of mobilestation #2 to the NACK of mobile station #1 (i.e., the Euclideandistance from (1+j)/√2) by the synchronous detection in the basestation, is represented by equation 2. That is, when mobile station #1transmits a NACK and mobile station #2 transmits an ACK, significantinter-code interference may be given from the ACK of mobile station #2to the NACK of mobile station #1.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 2} \right)\mspace{610mu}} & \; \\{{{\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( {1 - \frac{h_{1} - h_{2}}{h_{1} + h_{2}}} \right)} = {\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( \frac{2h_{2}}{h_{1} + h_{2}} \right)}}\mspace{14mu}} & \lbrack 2\rbrack\end{matrix}$

Similarly, when mobile station #1 and mobile station #2 both transmit aNACK signal, as shown in equation 3, inter-code interference does notoccur between the NACK of mobile station #1 and the NACK of mobilestation #2. Also, when mobile station #1 transmits an ACK and mobilestation #2 transmits a NACK, as shown in equation 4, significantinter-code interference may be given from the NACK of mobile station #2to the ACK of mobile station #1.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 3} \right)\mspace{610mu}} & \; \\{{{\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( {1 - \frac{h_{1} + h_{2}}{h_{1} + h_{2}}} \right)} = 0}\mspace{14mu}} & \lbrack 3\rbrack \\{\left( {{Equation}\mspace{14mu} 4} \right)\mspace{610mu}} & \; \\{{{\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( {{- 1} - \frac{{- h_{1}} + h_{2}}{h_{1} + h_{2}}} \right)} = {\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( \frac{{- 2}h_{2}}{h_{1} + h_{2}} \right)}}\mspace{14mu}} & \lbrack 4\rbrack\end{matrix}$

Here, taking into account that ARQ is applied to downlink data, 3GPP-LTEdefines that the target error rate per downlink data transmission isaround 1 to 10%. That is, in ARQ of downlink data, the ACK occurrencerate is significantly higher than the NACK occurrence rate. For example,in a mobile communication system in which the target error rate perdownlink data transmission is set to 10%, the ACK occurrence rate is90%, while the NACK occurrence rate is 10%. Therefore, in the aboveexample, there is a high possibility that a response signal of mobilestation #2 that interferes with a response signal of mobile station #1is an ACK. That is, there is a high possibility that, when mobilestation #1 transmits a NACK, significant inter-code interference(represented by equation 2) is given from a response signal of mobilestation #2 to this NACK, while there is a low possibility that, whenmobile station #1 transmits an ACK, significant inter-code interference(represented by equation 4) is given from a response signal of mobilestation #2 to this ACK. That is, there is a possibility that a NACK ismore influenced by interference than an ACK. Consequently, thepossibility of an increased error rate by interference becomes larger ina NACK than an ACK. Therefore, up till now, there is a possibility thata large difference is produced between NACK received quality and ACKreceived quality and a NACK is received in much poorer quality than anACK.

In view of the above, it is therefore an object of the present inventionto provide a radio communication apparatus and constellation controlmethod that can make ACK received quality and NACK received qualityequal.

Means for Solving the Problem

The radio communication apparatus of the present invention employs aconfiguration having: a first spreading section that performs firstspreading of a response signal using one of a plurality of firstsequences that can be separated from each other because of differentcyclic shift values; a second spreading section that performs secondspreading of the response signal subjected to the first spreading usingone of a plurality of second sequences that are orthogonal to eachother; and a rotating section that, with reference to a firstconstellation of a first response signal group formed with responsesignals subject to the first spreading by a part of the plurality offirst sequences, rotates a second constellation of a second responsesignal group formed with response signals subject to the first spreadingby other first sequences than the part of the plurality of firstsequences, by ninety degrees.

The constellation control method of the present invention includes: afirst spreading step of performing first spreading of a response signalusing one of a plurality of first sequences that can be separated fromeach other because of different cyclic shift values; a second spreadingstep of performing second spreading of the response signal subjected tothe first spreading using one of a plurality of second sequences thatare orthogonal to each other; and a rotating step of, with reference toa first constellation of a first response signal group formed withresponse signals subject to the first spreading by a part of theplurality of first sequences, rotating a second constellation of asecond response signal group formed with response signals subject to thefirst spreading by other first sequences than the part of the pluralityof first sequences, by ninety degrees.

Advantageous Effect of Invention

According to the present invention, it is possible to make ACK receivedquality and NACK received quality equal.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a spreading method of a response signal andreference signal (prior art);

FIG. 2 is a diagram showing the definition of PUCCH (prior art);

FIG. 3 illustrates a BPSK constellation (prior art);

FIG. 4 illustrates a QPSK constellation (prior art);

FIG. 5 is a block diagram showing the configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 6 is a block diagram showing the configuration of a mobile stationaccording to Embodiment 1 of the present invention;

FIG. 7 is a diagram showing a constellation change according toEmbodiment 1 of the present invention;

FIG. 8 illustrates a BPSK constellation according to Embodiment 1 of thepresent invention;

FIG. 9 illustrates a QPSK constellation according to Embodiment 1 of thepresent invention;

FIG. 10 is a diagram showing scrambling processing according toEmbodiment 1 of the present invention;

FIG. 11 is a diagram showing a constellation change according toEmbodiment 2 of the present invention;

FIG. 12 is a block diagram showing the configuration of a mobile stationaccording to Embodiment 3 of the present invention;

FIG. 13 is a diagram showing scrambling processing according toEmbodiment 4 of the present invention;

FIG. 14 is a block diagram showing the configuration of a mobile stationaccording to Embodiment 4 of the present invention;

FIG. 15 is a diagram showing a constellation change according toEmbodiment 5 of the present invention;

FIG. 16 is a diagram showing a constellation change according toEmbodiment 6 of the present invention;

FIG. 17 illustrates a BPSK constellation according to Embodiment 6 ofthe present invention;

FIG. 18 illustrates a BPSK constellation according to Embodiment 6 ofthe present invention;

FIG. 19 illustrates a QPSK constellation according to Embodiment 6 ofthe present invention;

FIG. 20 illustrates a QPSK constellation according to Embodiment 6 ofthe present invention;

FIG. 21 illustrates a QPSK constellation according to Embodiment 8 ofthe present invention;

FIG. 22 is a diagram showing a Q-axis amplitude in a case where thesynchronous detection output of mobile station #1 is rotated to theright direction by 45 degrees, according to Embodiment 9 of the presentinvention; and

FIG. 23 is a diagram showing a Q-axis amplitude in a case where thesynchronous detection output of mobile station #1 is rotated to theright direction by 45 degrees when all mobile stations use the sameconstellation.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained below in detailwith reference to the accompanying drawings.

(Embodiment 1)

FIG. 5 illustrates the configuration of base station 100 according tothe present invention, and FIG. 6 illustrates the configuration ofmobile station 200 according to the present embodiment.

Here, to avoid complicated explanation, FIG. 5 illustrates componentsassociated with transmission of downlink data and components associatedwith reception of uplink response signals to downlink data, which areclosely related to the present invention, and illustration andexplanation of the components associated with reception of uplink datawill be omitted. Similarly, FIG. 6 illustrates components associatedwith reception of downlink data and components associated withtransmission of uplink response signals to downlink data, which areclosely related to the present invention, and illustration andexplanation of the components associated with transmission of uplinkdata will be omitted.

Also, a case will be described with the following explanation, where ZACsequences are used for first spreading and block-wise spreading codesequences are used for second spreading. Here, for first spreading, itis equally possible to use sequences, which can be separated from eachother because of different cyclic shift values, other than ZACsequences. For example, for first spreading, it is possible to use a GCL(Generated Chip like) sequence, CAZAC (Constant Amplitude Zero AutoCorrelation) sequence, ZC (Zadoff-Chu) sequence or PN sequence such as aM sequence and orthogonal Gold code sequence. Also, as block-wisespreading code sequences for second spreading, it is possible to use anysequences as long as these sequences are orthogonal or substantiallyorthogonal to each other. For example, it is possible to use Walshsequences or Fourier sequences as block-wise spreading code sequencesfor second spreading.

Also, in the following explanation, twelve ZAC sequences with sequencelength of 12 and of cyclic shift values “0” to “11” are referred to as“ZAC #0” to “ZAC #11,” and three block-wise spreading code sequenceswith a sequence length of 4 and of sequence numbers “0” to “2” arereferred to as “BW #0” to “BW #3.” Here, the present invention is notlimited to these sequence lengths.

Also, in the following explanation, the PUCCH numbers are determined bythe cyclic shift values of ZAC sequences and the sequence numbers ofblock-wise spreading code sequences. That is, a plurality of resourcesfor response signals are determined by ZAC #0 to ZAC #11, which can beseparated from each other because of different cyclic shift values, andBW #0 to BW #2, which are orthogonal to each other.

Also, in the following explanation, the CCE numbers and the PUCCHnumbers are associated on a one-to-one basis. That is, CCE #0 is mappedto PUCCH #0, CCE #1 is mapped to PUCCH #1, CCE #2 is mapped to PUCCH #2. . . , and so on.

In base station 100 shown in FIG. 5, control information generatingsection 101 and mapping section 104 receive as input a resourceallocation result of downlink data. Also, control information generatingsection 101 and encoding section 102 receives as input a coding rate ofcontrol information to report the resource allocation result of downlinkdata, on a per mobile station basis, as coding rate information. Here,in the same way as above, the coding rate of the control information isone of ⅔, ⅓, ⅙ or 1/12.

Control information generating section 101 generates control informationto carry the resource allocation result, on a per mobile station basis,and outputs the control information to encoding section 102. Controlinformation, which is provided per mobile station, includes mobilestation ID information to indicate to which mobile station the controlinformation is directed. For example, control information includes, asmobile station ID information, CRC bits masked by the ID number of themobile station, to which control information is reported. Further,according to the coding rate information received as input, controlinformation generating section 101 allocates a L1/L2 CCH to each mobilestation based on the number of CCEs required to report the controlinformation, and outputs the CCE number corresponding to the allocatedL1/L2 CCH to mapping section 104. Here, in the same way as above, aL1/L2 CCH occupies one CCE when the coding rate of control informationis ⅔. Therefore, a L1/L2 CCH occupies two CCEs when the coding rate ofcontrol information is ⅓, a L1/L2 CCH occupies four CCEs when the codingrate of control information is ⅙, and a L1/L2 CCH occupies eight CCEswhen the coding rate of control information is 1/12. Also, in the sameway as above, when one L1/L2 CCH occupies a plurality of CCEs, the CCEsoccupied by the L1/L2 CCH are consecutive.

Encoding section 102 encodes control information on a per mobile stationbasis according to the coding rate information received as input, andoutputs the encoded control information to modulating section 103.

Modulating section 103 modulates the encoded control information andoutputs the result to mapping section 104.

On the other hand, encoding section 105 encodes the transmission datafor each mobile station (i.e., downlink data) and outputs the encodedtransmission data to retransmission control section 106.

Upon initial transmission, retransmission control section 106 holds theencoded transmission data on a per mobile station basis and outputs thedata to modulating section 107. Retransmission control section 106 holdstransmission data until retransmission control section 106 receives asinput an ACK of each mobile station from deciding section 117. Further,upon receiving as input a NACK of each mobile station from decidingsection 117, that is, upon retransmission, retransmission controlsection 106 outputs the transmission data associated with that NACK tomodulating section 107.

Modulating section 107 modulates the encoded transmission data receivedas input from retransmission control section 106, and outputs the resultto mapping section 104.

Upon transmission of control information, mapping section 104 maps thecontrol information received as input from modulating section 103 on aphysical resource based on the CCE number received as input from controlinformation generating section 101, and outputs the result to IFFTsection 108. That is, mapping section 104 maps control information onthe subcarrier corresponding to the CCE number in a plurality ofsubcarriers comprised of an orthogonal frequency division multiplexing(OFDM) symbol, on a per mobile station basis.

On the other hand, upon transmission of downlink data, mapping section104 maps the transmission data, which is provided on a per mobilestation basis, on a physical resource based on the resource allocationresult, and outputs the result to IFFT section 108. That is, based onthe resource allocation result, mapping section 104 maps transmissiondata on a subcarrier in a plurality of subcarriers comprised of an OFDMsymbol, on a per mobile station basis.

IFFT section 108 generates an OFDM symbol by performing an IFFT of aplurality of subcarriers on which control information or transmissiondata is mapped, and outputs the OFDM symbol to CP (Cyclic Prefix)attaching section 109.

CP attaching section 109 attaches the same signal as the signal at thetail end part of the OFDM symbol, to the head of the OFDM symbol as aCP.

Radio transmitting section 110 performs transmission processing such asdigital-to-analog (D/A) conversion, amplification and up-conversion onthe OFDM symbol with a CP and transmits the result from antenna 111 tomobile station 200 (in FIG. 6).

On the other hand, radio receiving section 112 receives a responsesignal or reference signal transmitted from mobile station 200 (in FIG.6), via antenna 111, and performs receiving processing such asdown-conversion and analog-to-digital (A/D) conversion on the responsesignal or reference signal.

CP removing section 113 removes the CP attached to the response signalor reference signal subjected to receiving processing.

Despreading section 114 despreads the response signal by a block-wisespreading code sequence that is used for second spreading in mobilestation 200, and outputs the despread response signal to correlationprocessing section 115. Similarly, despreading section 114 despreads thereference signal by an orthogonal sequence that is used to spread thereference signal in mobile station 200, and outputs the despreadreference signal to correlation processing section 115.

Correlation processing section 115 finds the correlation value betweenthe spread response signal, spread reference signal and ZAC sequencethat is used for first spreading in mobile station 200, and outputs thecorrelation value to descrambling section 116.

Descrambling section 116 descrambles the correlation value by thescrambling code associated with the cyclic shift value of the ZACsequence, and outputs the descrambled correlation value to decidingsection 117.

Deciding section 117 detects a response signal on a per mobile stationbasis, by detecting a correlation peak on a per mobile station basisusing detection windows. For example, upon detecting a correlation peakin the detection window for mobile station #1, deciding section 117detects a response signal from mobile station #1. Then, deciding section117 decides whether the detected response signal is an ACK or NACK bythe synchronous detection using the correlation value of the referencesignal, and outputs the ACK or NACK to retransmission control section106 on a per mobile station basis.

On the other hand, in mobile station 200 shown in FIG. 6, radioreceiving section 202 receives the OFDM symbol transmitted from basestation 100 (in FIG. 5), via antenna 201, and performs receivingprocessing such as down-conversion and A/D conversion on the OFDMsymbol.

CP removing section 203 removes the CP attached to the OFDM symbolsubjected to receiving processing.

FFT (Fast Fourier Transform) section 204 acquires control information ordownlink data mapped on a plurality of subcarriers by performing a FFTof the OFDM symbol, and outputs the control information or downlink datato extracting section 205.

Extracting section 205 and decoding section 207 receives as input codingrate information indicating the coding rate of the control information,that is, information indicating the number of CCEs occupied by a L1/L2CCH.

Upon reception of the control information, based on the coding rateinformation, extracting section 205 extracts the control informationfrom the plurality of subcarriers and outputs it to demodulating section206.

Demodulating section 206 demodulates the control information and outputsthe demodulated control information to decoding section 207.

Decoding section 207 decodes the control information based on the codingrate information received as input, and outputs the decoded controlinformation to deciding section 208.

On the other hand, upon receiving the downlink data, extracting section205 extracts the downlink data directed to the mobile station from theplurality of subcarriers, based on the resource allocation resultreceived as input from deciding section 208, and outputs the downlinkdata to demodulating section 210. This downlink data is demodulated indemodulating section 210, decoded in decoding section 211 and receivedas input in CRC section 212.

CRC section 212 performs an error detection of the decoded downlink datausing a CRC, generates an ACK in the case of CRC=OK (i.e., when no erroris found) and a NACK in the case of CRC=NG (i.e., when error is found),as a response signal, and outputs the generated response signal tomodulating section 213. Further, in the case of CRC=OK (i.e., when noerror is found), CRC section 212 outputs the decoded downlink data asreceived data.

Deciding section 208 performs a blind detection of whether or not thecontrol information received as input from decoding section 207 isdirected to the mobile station. For example, deciding section 208decides that, if CRC=OK is found (i.e., if no error is found) as aresult of demasking by the ID number of the mobile station, the controlinformation is directed to the mobile station. Further, deciding section208 outputs the control information for the mobile station, that is, theresource allocation result of downlink data for the mobile station, toextracting section 205.

Further, deciding section 208 decides a PUCCH to use to transmit aresponse signal from the mobile station, from the CCE number associatedwith subcarriers on which the control information directed to the mobilestation is mapped, and outputs the decision result (i.e., PUCCH number)to control section 209. For example, in the same way as above, when theCCE corresponding to subcarriers, on which control information directedto the mobile station is mapped, is CCE #0, deciding section 208 decidesPUCCH #0 associated with CCE #0 as the PUCCH for the mobile station.Also, for example, when CCEs corresponding to subcarriers on whichcontrol information directed to the mobile station is mapped are CCE #0to CCE #3, deciding section 208 decides PUCCH #0 associated with CCE #0,which is the smallest number in CCE #0 to CCE #3, as the PUCCH for themobile station, and, when CCEs corresponding to subcarriers on whichcontrol information directed to the mobile station is mapped are CCE #4to CCE #7, deciding section 208 decides PUCCH #4 associated with CCE #4,which is the smallest number in CCE #0 to CCE #3, as the PUCCH for themobile station.

Based on the PUCCH number received as input from deciding section 208,control section 209 controls the cyclic shift value of a ZAC sequencethat is used for first spreading in spreading section 215 and ablock-wise spreading code sequence that is used for second spreading inspreading section 218. That is, control section 209 selects a ZACsequence of the cyclic shift value corresponding to the PUCCH numberreceived as input from deciding section 208, amongst ZAC #0 to ZAC #11,and sets the selected ZAC sequence in spreading section 215, and selectsthe block-wise spreading code sequence corresponding to the PUCCH numberreceived as input from deciding section 208, amongst BW #0 to BW #2, andsets the selected block-wise spreading code sequence in spreadingsection 218. That is, control section 209 selects one of a plurality ofresources defined by ZAC #0 to ZAC #11 and BW #0 to BW #2. Also, controlsection 209 reports the selected ZAC sequence to scrambling section 214.

Further, control section 209 controls a block-wise spreading codesequence that is used for second spreading in spreading section 223.That is, control section 209 sets the block-wise spreading code sequencecorresponding to the PUCCH number received as input from decidingsection 208, in spreading section 223.

Modulating section 213 modulates the response signal received as inputfrom CRC section 212 and outputs the result to spreading section 214.Modulation processing in modulating section 213 will be described laterin detail.

Scrambling section 214 multiplies the modulated response signal (i.e.,response symbol) by a scrambling code “1” or “e^(−j(π/2))” depending onto the ZAC sequence selected in control section 209, and outputs theresponse signal multiplied by the scrambling code to spreading section215. Here, by multiplication of the scrambling code “e^(−j(π/2),” theconstellation of the response signal is rotated by −90 degrees. Thus,scrambling section 214 functions as a rotation means to rotate theconstellation of a response signal. Scrambling processing in scramblingsection 214 will be described later in detail.

Spreading section 215 performs first spreading of the response signaland reference signal (i.e., reference symbol) by the ZAC sequence set incontrol section 209, and outputs the response signal subjected to firstspreading to IFFT section 216 and the reference signal subjected tofirst spreading to IFFT section 221.

IFFT section 216 performs an IFFT of the response signal subjected tofirst spreading, and outputs the response signal subjected to IFFT to CPattaching section 217.

CP attaching section 217 attaches the same signal as the signal at thetail end part of the response signal subjected to an IFFT, to the headof the response signal as a CP.

Spreading section 218 performs second spreading of the response signalwith a CP by the block-wise spreading code sequence set in controlsection 209, and outputs the response signal subjected to secondspreading, to multiplexing section 219.

IFFT section 221 performs an IFFT of the reference signal subjected tofirst spreading, and outputs the reference signal subjected to IFFT toCP attaching section 222.

CP attaching section 222 attaches the same signal as the signal at thetail end part of the reference signal subjected to IFFT, to the head ofthe reference signal.

Spreading section 223 performs second spreading of the reference signalwith a CP by the block-wise spreading code sequence set in controlsection 209, and outputs the reference signal subjected to secondspreading, to multiplexing section 219.

Multiplexing section 219 time-multiplexes the response signal subjectedto second spreading and the reference signal subjected to secondspreading in one slot, and outputs the result to radio transmittingsection 220.

Radio transmitting section 220 performs transmission processing such asD/A conversion, amplification and up-conversion on the response signalsubjected to second spreading or the reference signal subjected tosecond spreading, and transmits the resulting signal from antenna 201 tobase station 100 (in FIG. 5).

Next, modulation processing in modulating section 213 and scramblingprocessing in scrambling section 214 will be explained in detail.

In a plurality of response signals subject to second spreading by thesame block-wise spreading code sequence, inter-code interference on thecyclic shift axis is the largest between the response signals that arelocated on the closest positions to each other on the cyclic shift axis.For example, in six response signals subject to second spreading by BW#0 in FIG. 2, the response signal that is transmitted using PUCCH #1 issubject to the largest interference from the response signal that istransmitted using PUCCH #0 and the response signal that is transmittedusing PUCCH #2.

Also, the ACK occurrence rate is significantly higher than the NACKoccurrence rate, and, consequently, when a NACK is transmitted using anarbitrary PUCCH, there is a high possibility that a response signal thatgives interference to the PUCCH is an ACK. Therefore, to improve theerror rate performance of a NACK, it is important to reduce interferencefrom an ACK.

With the present embodiment, as shown in FIG. 7, the constellation ofeach response signal is rotated on the cyclic shift axis.

To be more specific, referring to six response signals subject to secondspreading by BW #0 in FIG. 7, the constellation acquired by rotating theconstellation of a response signal that is transmitted using PUCCH #0,by −90 degrees, is used as the constellation of a response signal thatis transmitted using PUCCH #1, and the constellation acquired byrotating the constellation of the response signal that is transmittedusing PUCCH #1, by +90 degrees, is used as the constellation of aresponse signal that is transmitted using PUCCH #2. The same applies toPUCCH #2 to PUCCH #5. For example, when the modulation scheme ofresponse signals is BPSK, constellation #1 of PUCCH #0, PUCCH #2 andPUCCH #4 is as shown in FIG. 3, while constellation #2 of PUCCH #1,PUCCH #3 and PUCCH #5 is as shown in FIG. 8. Also, for example, when themodulation scheme of response signals is QPSK, constellation #1 of PUCCH#0, PUCCH #2 and PUCCH #4 is as shown in FIG. 4, while constellation #2of PUCCH #1, PUCCH #3 and PUCCH #5 is as shown in FIG. 9.

Thus, according to the present embodiment, in ZAC #0, ZAC #2, ZAC #4,ZAC #6, ZAC #8 and ZAC #10 that are used for first spreading of responsesignals subject to second spreading by BW #0, response signals subjectto first spreading by ZAC #0, ZAC #4 and ZAC #8 form the first responsesignal group, and response signals subject to first spreading by ZAC #2,ZAC #6 and ZAC #10 form the second response signal group. That is,according to the present embodiment, the response signals belonging tothe first response signal group and the response signals belonging tothe second response signal group are alternately allocated on the cyclicshift axis. While the constellation of the first response signal groupis referred to as “constellation #1” (in FIG. 3 and FIG. 4), theconstellation of the second response signal group is referred to as“constellation #2” (in FIG. 8 and FIG. 9). That is, according to thepresent embodiment, the constellation of the second response signalgroup is rotated by −90 degrees with respect to the constellation of thefirst response signal group.

Also, according to the present embodiment, as shown in FIG. 10, therotation of constellation is performed by scrambling processing inscrambling section 214.

That is, when the modulation scheme of response signals is BPSK,modulating section 213 modulates the response signals usingconstellation #1 shown in FIG. 3. Therefore, the signal point of an ACKis (−1/√2, −1/√2), and the signal point of a NACK is (1/√2, 1/√2). Also,the signal point of a reference signal received as input from spreadingsection 215 is the same as the signal point of a NACK, (1/√2, 1/√2).

Then, in response signals subject to second spreading using BW #0,scrambling section 214 multiplies a response signal subject to firstspreading using ZAC #0, ZAC #4 or ZAC #8 by scrambling code “1,” andmultiples a response signal subject to first spreading using ZAC #2, ZAC#6 or ZAC #10 by scrambling code “e^(−j(π/2)).” Therefore, for theresponse signal subject to first spreading by ZAC #0, ZAC #4 or ZAC #8,the signal point of an ACK is (−1/√2, −1/√2) and the signal point of aNACK is (1/√2, 1/√2). That is, the constellation of the response signalsubject to first spreading by ZAC #0, ZAC #4 or ZAC #8 is constellation#1 (in FIG. 3). On the other hand, for the response signal subject tofirst spreading by ZAC #2, ZAC #6 or ZAC #10, the signal point of an ACKis (−1/√2, 1/√2) and the signal point of a NACK is (1/√2, −1/√2). Thatis, the constellation of the response signal subject to first spreadingby ZAC #2, ZAC #6 or ZAC #10 is constellation #2 (in FIG. 8).

Thus, according to the present embodiment, by scrambling processing inscrambling section 214, the constellation of the second response signalgroup is rotated by −90 degrees with respect to the constellation of thefirst response signal group.

As described above, an example case will be described below where mobilestation #1 transmits a response signal using PUCCH #1 (in FIG. 7) andanother mobile station #2 transmits a response signal using PUCCH #0 (inFIG. 7). Here, constellation #2 (in FIG. 8) is used for the responsesignal of mobile station #1, and constellation #1 (in FIG. 3) is usedfor the response signal of mobile station #2.

When mobile station #1 and mobile station #2 both transmit an ACK andthe base station receives the response signal from mobile station #1,interference given from the response signal of mobile station #2 to theresponse signal of mobile station #1 is as follows.

That is, when the ACK and reference signal transmitted from mobilestation #1 are received by the base station via a channel, in the basestation, a response signal represented by (−1+j) h1/√2 and referencesignal represented by (1+j) h1/√2 are found as a correlation output ofmobile station #1.

Also, when the ACK and reference signal transmitted from mobile station#2 are received by the base station via a channel, in the base station,a component represented by (−1−j) h2/√2 is found as interference to theresponse signal of mobile station #1 and a component represented by(1+j) h2/√2 is found as interference to the reference signal of mobilestation #1 in the correlation output of mobile station #1.

Therefore, when the ACK from mobile station #1 and the ACK from mobilestation #2 are code-multiplexed, in the base station, a response signalrepresented by (1+j)(jh1−h2)/√2 and reference signal represented by(1+j)(h1+h2)/√2 are found in the correlation output of mobile station#1.

Therefore, the interference component given from the ACK of mobilestation #2 to the ACK of mobile station #1 (i.e., the Euclidean distancefrom (−1+j)/√2) by the synchronous detection in the base station, isrepresented by equation 5.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 5} \right)\mspace{610mu}} & \; \\{{{\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( {j - \frac{{jh}_{1} - h_{2}}{h_{1} + h_{2}}} \right)} = {\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( \frac{\left( {1 + j} \right)h_{2}}{h_{1} + h_{2}} \right)}}\mspace{11mu}} & \lbrack 5\rbrack\end{matrix}$

Also, when mobile station #1 transmits a NACK, mobile station #2transmits an ACK and the base station receives the response signal frommobile station #1, interference given from the response signal of mobilestation #2 to the response signal of mobile station #1 is as follows.

That is, when the NACK and reference signal transmitted from mobilestation #1 are received by the base station via a channel, in the basestation, a response signal represented by (1−j) h1/√2 and referencesignal represented by (1+j) h1/√2 are found as a correlation output ofmobile station #1.

Also, when the ACK and reference signal transmitted from mobile station#2 are received by the base station via a channel, in the base station,a component represented by (−1−j) h2/√2 is found as interference to theresponse signal of mobile station #1 and a component represented by(1+j) h2/√2 is found as interference to the reference signal of mobilestation #1 in the correlation output of mobile station #1.

Therefore, when the NACK from mobile station #1 and the ACK from mobilestation #2 are code-multiplexed, in the base station, a response signalrepresented by (1+j)(−jh1+h2)/√2 and reference signal represented by(1+j)(h1+h2)/√2 are found in the correlation output of mobile station#1.

Therefore, the interference component given from the ACK of mobilestation #2 to the NACK of mobile station #1 (i.e., the Euclideandistance from (1−j)/√2) by the synchronous detection in the basestation, is represented by equation 6.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 6} \right)\mspace{610mu}} & \; \\{{{\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( {{- j} - \frac{{- {jh}_{1}} - h_{2}}{h_{1} + h_{2}}} \right)} = {\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( \frac{\left( {1 + j} \right)h_{2}}{h_{1} + h_{2}} \right)}}\mspace{31mu}} & \lbrack 6\rbrack\end{matrix}$

Similarly, according to the present embodiment, when both mobile station#1 and mobile station #2 transmit a NACK signal, the interferencecomponent given from the NACK of mobile station #2 to the NACK of mobilestation #1 (i.e., the Euclidean distance from (1−j)/√2) by thesynchronous detection in the base station, is as shown in equation 7.Also, according to the present invention, when mobile station #1transmits an ACK and mobile station #2 transmits a NACK, theinterference component given from the NACK of mobile station #2 to theACK of mobile station #1 (i.e., the Euclidean distance from (−1+j)/√2)by the synchronous detection in the base station, is as shown inequation 8.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 7} \right)\mspace{610mu}} & \; \\{{{\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( {{- j} - \frac{{- {jh}_{1}} + h_{2}}{h_{1} + h_{2}}} \right)} = {\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( \frac{\left( {{- 1} - j} \right)h_{2}}{h_{1} + h_{2}} \right)}}\mspace{14mu}} & \lbrack 7\rbrack \\{\left( {{Equation}\mspace{14mu} 8} \right)\mspace{610mu}} & \; \\{{{\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( {j - \frac{{jh}_{1} + h_{2}}{h_{1} + h_{2}}} \right)} = {\frac{\left( {1 + j} \right)}{\sqrt{2}}\left( \frac{\left( {{- 1} + j} \right)h_{2}}{h_{1} + h_{2}} \right)}}\mspace{14mu}} & \lbrack 8\rbrack\end{matrix}$

When the interference components represented by equation 5 to equation 8are compared, it is understood that the magnitudes of the interferencecomponents represented by equation 5 to equation 8 are the same. Thatis, according to the present embodiment, regardless of the ACKoccurrence rate or the NACK occurrence rate, it is possible to make theerror rate of an ACK and the error rate of a NACK equal. Therefore,according to the present embodiment, it is possible to make ACK receivedquality and NACK received quality equal.

Also, according to the present embodiment, scrambling section 214 maymultiply a modulated response signal by a scrambling code of “1” or“e^(j(π/2)),” and rotate the constellation of the second response signalgroup by +90 degrees with respect to the constellation of the firstresponse signal group.

(Embodiment 2)

With the present embodiment, for example, while the constellation isrotated in cell #1 as shown in FIG. 7, the constellation is rotated incell #2 adjacent to cell #1 as shown in FIG. 11. Therefore, for example,referring to PUCCH #1, while constellation #2 (in FIG. 8 and FIG. 9) isused for PUCCH #1 in cell #1, constellation #1 (in FIG. 3 and FIG. 4) isused for PUCCH #1 in cell #2. Similarly, referring to PUCCH #2, whileconstellation #1 (in FIG. 3 and FIG. 4) is used for PUCCH #2 in cell #1,constellation #2 (in FIG. 8 and FIG. 9) is used for PUCCH #2 in cell #2.

That is, with the present invention, further to Embodiment 1, betweentwo adjacent cells, the constellation of one of two response signalssubject to first spreading by ZAC sequences of the same cyclic shiftvalue, is rotated by 90 degrees with respect to the constellation of theother response signal.

By this means, between a plurality of adjacent cells, it is possible torandomize interference between a plurality of response signals subjectto first spreading by ZAC sequences of the same cyclic shift value. Thatis, according to the present embodiment, it is possible to randomize andreduce inter-cell interference between response signals.

(Embodiment 3)

With the present embodiment, the constellation is rotated uponmodulation of response signals.

FIG. 12 illustrates the configuration of mobile station 400 according tothe present embodiment. Here, in FIG. 12, the same components as in FIG.6 (Embodiment 1) will be assigned the same reference numerals and theirexplanation will be omitted.

In mobile station 400, a ZAC sequence selected in control section 209 isreported to modulating section 401.

Then, in response signals subject to second spreading using BW #0 shownin FIG. 7, modulating section 401 modulates a response signal subject tofirst spreading by ZAC #0, ZAC #4 or ZAC #8 (i.e., first response signalgroup) using constellation #1 (in FIG. 3 and FIG. 4), and modulates aresponse signal subject to first spreading by ZAC #2, ZAC #6 or ZAC #10(i.e., second response signal group) using constellation #2 (in FIG. 8and FIG. 9).

Thus, according to the present embodiment, upon modulation processing inmodulating section 401, the constellation of the second response signalgroup is rotated by 90 degrees with respect to the constellation of thefirst response signal group. That is, according to the presentembodiment, modulating section 401 functions as a modulating means thatmodulates a response signal and as a rotating means that rotates theconstellation of the response signal. Therefore, the present embodimentdoes not require scrambling section 214 (in FIG. 6) and descramblingsection 116 (in FIG. 5) in Embodiment 1.

Thus, by performing rotation processing in modulating section 401instead of scrambling section 214, it is possible to achieve the sameeffect as in Embodiment 1.

(Embodiment 4)

Embodiments 1 to 3 rotate the constellation of a response signal withoutchanging the constellation of a reference signal. By contrast with this,as shown in FIG. 13, the present embodiment rotates the constellation ofa reference signal without changing the constellation of a responsesignal.

FIG. 14 illustrates the configuration of mobile station 600 according tothe present embodiment. Here, in FIG. 14, the same components as in FIG.6 (Embodiment 1) will be assigned the same reference numerals and theirexplanation will be omitted.

In mobile station 600, when the modulation scheme of response signals isBPSK, scrambling section 214 multiplies a reference signal subject tofirst spreading using ZAC #0, ZAC #4 or ZAC #8 by “1,” and multiples areference signal subject to first spreading using ZAC #2, ZAC #6 or ZAC#10 by “e^(−j(π/2)).” Therefore, the signal point of a reference signalsubject to first spreading by ZAC #0, ZAC #4 or ZAC #8 is (1/√2, 1/√2),and the signal point of a reference signal subject to first spreading byZAC #2, ZAC #6 or ZAC #10 is (1/√2, −1/√2).

Thus, by scrambling processing in scrambling section 214, the presentembodiment rotates the constellation of a reference signal for thesecond response signal group by −90 degrees with respect to theconstellation of a reference signal for the first response signal group.

Thus, by performing rotation processing of the constellation of areference signal in scrambling section 214, it is equally possible toachieve the same effect as in Embodiment 1.

Also, according to the present embodiment, scrambling section 214 maymultiply a reference signal by a scrambling code of “1” or “e^(j(π/2)),”and rotate the constellation of a reference signal for the firstresponse signal group by +90 degrees with respect to the constellationof a reference signal for the second response signal group.

(Embodiment 5)

If there is a large difference of received power between responsesignals from a plurality of mobile stations in a base station, responsesignals of the higher received power may interfere with response signalsof the lower received power. For example, in response signals subject tosecond spreading using BW #0 shown in FIG. 15, when the received powerof a response signal that is transmitted using PUCCH #0 and receivedpower of a response signal that is transmitted using PUCCH #3 arehigher, and the received power of response signals that are transmittedusing the other PUCCHs are lower, the response signal that istransmitted using PUCCH #0 and the response signal that is transmittedusing PUCCH #3 give the largest interference to the response signalsthat are transmitted using the other PUCCHs.

Therefore, in this case, in ZAC #0, ZAC #2, ZAC #4, ZAC #6, ZAC #8 andZAC #10 that are used for first spreading of response signals subject tosecond spreading using BW #0, the response signals subject to firstspreading by ZAC #0 and ZAC #6 form the first response signal group, andthe response signals subject to first spreading by ZAC #2, ZAC #4, ZAC#8 and ZAC #10 form the second response signal group. Then, while theconstellation of the first response signal group is constellation #1 (inFIG. 3 and FIG. 4), the constellation of the second response signalgroup is constellation #2 (in FIG. 8 and FIG. 9). That is, the presentembodiment rotates the constellation of the second response signal groupof the lower received power by −90 degrees with respect to theconstellation of the first response signal group of the higher receivedpower.

Also, the present embodiment may rotate the constellation of the secondresponse signal group of the lower received power by +90 degrees withrespect to the constellation of the first response signal group of thehigher received power.

Thus, according to the present embodiment, by rotating the constellationof a signal of the lower received power by 90 degrees with respect tothe constellation of a response signal of the higher received power onthe cyclic shift axis, it is possible to prevent an increased NACK errorrate by inter-code interference from an ACK due to the received powerdifference, and, as in Embodiment 1, make the ACK error rate and NACKerror rate equal.

(Embodiment 6)

A case will be explained with the present embodiment where twelve PUCCHsshown in FIG. 16 are defined.

In this case, referring to four response signals subject to secondspreading by BW #0 in FIG. 16, the constellation acquired by rotatingthe constellation of the response signal that is transmitted using PUCCH#0, by −90 degrees, is the constellation of the response signal that istransmitted using PUCCH #1, the constellation acquired by rotating theconstellation of the response signal that is transmitted using PUCCH #1,by −90 degrees, is the constellation of the response signal that istransmitted using PUCCH #2, and the constellation acquired by rotatingthe constellation of the response signal that is transmitted using PUCCH#2, by −90 degrees, is the constellation of the response signal that istransmitted using PUCCH #3.

For example, when the modulation scheme of response signals is BPSK,constellation #1 in PUCCH #0 is as shown in FIG. 3, constellation #2 inPUCCH #1 is as shown in FIG. 8, constellation #3 in PUCCH #2 is as shownin FIG. 17, and constellation #4 in PUCCH #3 is as shown in FIG. 18.Also, when the modulation scheme of response signals is QPSK,constellation #1 in PUCCH #0 is as shown in FIG. 4, constellation #2 inPUCCH #1 is as shown in FIG. 9, constellation #3 in PUCCH #2 is as shownin FIG. 19, and constellation #4 in PUCCH #3 is as shown in FIG. 20.

Thus, the present embodiment rotates the constellation of each responsesignal by −90 degrees on the cyclic shift axis. That is, although twoconstellations are used in Embodiment 1, four constellations are used inthe present embodiment. Therefore, according to the present embodiment,it is possible to further randomize interference between responsesignals than in Embodiment 1. That is, according to the presentembodiment, it is further possible to make the ACK error rate and NACKerror rate equal.

Also, the present embodiment may rotate the constellation of eachresponse signal by +90 degrees on the cyclic shift axis.

(Embodiment 7)

A case will be explained with the present embodiment where a basestation detects that a mobile station fails to receive controlinformation to carry the resource allocation result of downlink data.

The mobile station performs a blind detection of whether or not controlinformation is directed to the mobile station as described above, and,consequently, if the mobile station fails to receive control informationdue to poor channel condition, the mobile station has no way of knowingwhether or not downlink data directed to the mobile station has beentransmitted from the base station. Therefore, in this case, the mobilestation does not receive data nor transmit a response signal. Thus, whena response signal is not transmitted from the mobile station to the basestation, the base station needs to detect whether a response signal isnot transmitted from the mobile station, in addition to decide whetherthe response signal is an ACK or a NACK.

Here, non-transmission of a response signal from a mobile station isreferred to as “DTX (discontinuous transmission)”.

Normally, a threshold decision is used to detect DTX. That is, the basestation measures the received power of a PUCCH that is used to transmita response signal from the mobile station, detect DTX if the receivedpower is lower than a threshold, and decides that an ACK or a NACK istransmitted from the mobile station if the received power is equal to orhigher than the threshold.

However, PUCCHs are separated by using different cyclic shift values ofZAC sequences and block-wise spreading code sequences. If the delay in achannel is large, if the transmission timing of a mobile stationinvolves error or if transmission power control involves error,interference is significant especially on the cyclic shift axis.Therefore, if the base station tries to decide whether or not DTX isdetected by a threshold decision of power in these cases, decision erroris caused due to interference of leaked power from another mobilestation that transmits a response signal using the ZAC sequence of theadjacent cyclic shift value. For example, if mobile station #1 transmitsan ACK using ZAC #0 and mobile station #2 that should transmit aresponse signal using ZAC #1 fails to receive control information anddoes not transmit a response signal, the power of the response signalfrom mobile station #1 may leak even after correlation processing todetect a response signal from mobile station #2. In this case, aconventional technique cannot decide whether a response signal istransmitted using ZAC #1 or power leaks from ZAC #0.

Therefore, similar to Embodiment 1 (FIG. 7), the present embodimentrotates the constellation of each response signal on the cyclic shiftaxis.

As in Embodiment 1, an example case will be described below where mobilestation #1 transmits a response signal using PUCCH #1 (in FIG. 7) andanother mobile station #2 transmits a response signal using PUCCH #0 (inFIG. 7). Also, an example case will be described below where themodulation scheme of response signals is BPSK. Here, constellation #2(in FIG. 8) is used for a response signal of mobile station #1 andconstellation #1 (in FIG. 3) is used for a response signal of mobilestation #2.

When mobile station #1 and mobile station #2 both transmit an ACK andthe base station receives the response signal from mobile station #1,interference given from the response signal of mobile station #2 to theresponse signal of mobile station #1 is as follows.

That is, when the ACK and reference signal transmitted from mobilestation #1 are received by the base station via a channel, in the basestation, a response signal represented by (−1+j) h1/√2 and referencesignal represented by (1+j) h1/√2 are found as a correlation output ofmobile station #1.

Also, when the ACK and reference signal transmitted from mobile station#2 are received by the base station via a channel, in the base station,a component represented by (−1−j) h2/√ is found as interference to theresponse signal of mobile station #1 and a component represented by(1+j) h2/√2 is found as interference to the reference signal of mobilestation #1 in the correlation output of mobile station #1.

Therefore, when the ACK from mobile station #1 and ACK from mobilestation #2 are code-multiplexed, in the base station, a response signalrepresented by (1+j)(jh1−h2)/√2 and reference signal represented by(1+j)(h1+h2)/√2 are found in the correlation output of mobile station#1. That is, in this case, the output of synchronous detection in thebase station is as shown in equation 9.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 9} \right)\mspace{610mu}} & \; \\{\frac{{jh}_{1} - h_{2}}{h_{1} + h_{2}}\mspace{14mu}} & \lbrack 9\rbrack\end{matrix}$

Also, when mobile station #2 transmits an ACK and mobile station #1fails to receive control information and does not transmit a responsesignal, in the base station, a response signal represented by(1+j)(−h2)/√2 and reference signal represented by (1+j)(h2)/√2 are foundin the correlation output of mobile station #1. Therefore, in this case,the output of synchronous detection in the base station is as shown inequation 10.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 10} \right)\mspace{585mu}} & \; \\{\frac{- h_{2}}{h_{2}} = {- 1}} & \lbrack 10\rbrack\end{matrix}$

Comparing equation 9 and equation 10, it is understood that, when aresponse signal is provided from mobile station #1, there are thequadrature component (i.e., the value on the Q axis or complexcomponent) and in-phase component (i.e., the value on the I axis or realnumber component) in the synchronous detection output, while, when aresponse signal is not provided from mobile station #1, there is noquadrature component but is only the in-phase component in thesynchronous detection output.

Also, another example case will be described where mobile station #1transmits a response signal using PUCCH #2 (in FIG. 7) and anothermobile station #2 transmits a response signal using PUCCH #1 (in FIG.7). Here, constellation #1 (in FIG. 3) is used for the response signalof mobile station #1 and constellation #2 (in FIG. 8) is used for theresponse signal of mobile station #2.

When mobile station #1 and mobile station #2 both transmit an ACK andthe base station receives the response signal from mobile station #1,interference given from the response signal of mobile station #2 to theresponse signal of mobile station #1 is as follows.

That is, when the ACK and reference signal transmitted from mobilestation #1 are received by the base station via a channel, in the basestation, a response signal represented by (−1−j) h1/√2 and referencesignal represented by (1+j) h1/√2 are found as a correlation output ofmobile station #1.

Also, when the ACK and reference signal transmitted from mobile station#2 are received by the base station via a channel, in the base station,a component represented by (−1+j) h2/√2 is found as interference to theresponse signal of mobile station #1 and a component represented by(1+j) h2/√2 is found as interference to the reference signal of mobilestation #1 in the correlation output of mobile station #1.

Therefore, when the ACK from mobile station #1 and ACK from mobilestation #2 are code-multiplexed, in the base station, a response signalrepresented by (1+j)(−h1+jh2)/√2 and reference signal represented by(1+j)(h1+h2)/√2 are found in the correlation output of mobile station#1. That is, in this case, the output of synchronous detection in thebase station is as shown in equation 11.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 11} \right)\mspace{585mu}} & \; \\{\frac{{- h_{1}} + {jh}_{2}}{h_{1} + h_{2}}\mspace{14mu}} & \lbrack 11\rbrack\end{matrix}$

Also, when mobile station #2 transmits an ACK and mobile station #1fails to receive control information and does not transmit a responsesignal, in the base station, a response signal represented by(1+j)(jh2)/√2 and reference signal represented by (1+j)(h2)/√2 are foundin the correlation output of mobile station #1. Therefore, in this case,the output of synchronous detection in the base station is as shown inequation 12.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 12} \right)\mspace{585mu}} & \; \\{{\frac{{jh}_{2}}{h_{2}} = j}\mspace{14mu}} & \lbrack 12\rbrack\end{matrix}$

Comparing equation 11 and equation 12, it is understood that, when aresponse signal is provided from mobile station #1, there are thequadrature component and in-phase component in the synchronous detectionoutput, while, when a response signal is not provided from mobilestation #1, there is no quadrature component but is only the in-phasecomponent in the synchronous detection output.

Therefore, according to the present embodiment, a base station candecide whether or not DTX is detected for a response signal from amobile station, based on one of the magnitude of the in-phase componentand the magnitude of the quadrature component in the synchronousdetection output. Also, a response signal that is transmitted from amobile station using the ZAC sequence of an adjacent cyclic shift value,does not have a negative effect on the detection of DTX, so that, evenwhen there is significant interference from a response signaltransmitted from the mobile station using the ZAC sequence of theadjacent cyclic shift value, it is possible to identify DTX accurately.

(Embodiment 8)

Similar to Embodiment 7, a case will be explained with the presentembodiment where a base station detects that a mobile station fails toreceive control information to report a resource allocation result ofdownlink data.

Here, an example case will be described with the present embodimentwhere the modulation scheme of response signals is QPSK. Also, as inEmbodiment 1, an example case will be described where mobile station #1transmits a response signal using PUCCH #1 (in FIG. 7) and anothermobile station #2 transmits a response signal using PUCCH #0 (in FIG.7). Also, with the present embodiment, constellation #2 (in FIG. 21) isused for the response signal of mobile station #1 and constellation #1(in FIG. 4) is used for the response signal of mobile station #2.

When mobile station #1 and mobile station #2 both transmit a “ACK/ACK”and the base station receives the response signal from mobile station#1, interference given from the response signal of mobile station #2 tothe response signal of mobile station #1 is as follows.

That is, when the “ACK/ACK” and reference signal transmitted from mobilestation #1 are received by the base station via a channel, in the basestation, a response signal represented −h1 and reference signalrepresented by (1+j) h1/√2 are found as a correlation output of mobilestation #1.

Also, when the “ACK/ACK” and reference signal transmitted from mobilestation #2 are received by the base station via a channel, in the basestation, a component represented by (−1−j) h2/√2 is found asinterference to the response signal of mobile station #1 and componentrepresented by (1+j) h2/√2 is found as interference to the referencesignal of mobile station #1 in the correlation output of mobile station#1.

Therefore, when the “ACK/ACK” from mobile station #1 and “ACK/ACK” frommobile station #2 are code-multiplexed, in the base station, a responsesignal represented by {−√2h1−(1+j)h2}/√2 and reference signalrepresented by (1+j)(h1+h2)/√2 are found in the correlation output ofmobile station #1. That is, in this case, the output of synchronousdetection in the base station is as shown in equation 13.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 13} \right)\mspace{585mu}} & \; \\{\frac{{{- \sqrt{2}}h_{1}} - {\left( {1 + j} \right)h_{2}}}{\left( {1 + j} \right)\left( {h_{1} + h_{2}} \right)}\;} & \lbrack 13\rbrack\end{matrix}$

Also, when mobile station #2 transmits a “ACK/ACK” and mobile station #1fails to receive control information and does not transmit a responsesignal, in the base station, a response signal represented by(1+j)(−h2)/√2 and reference signal represented by (1+j)(h2)/√2 are foundin the correlation output of mobile station #1. Therefore, in this case,the output of synchronous detection in the base station is as shown inequation 14.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 14} \right)\mspace{585mu}} & \; \\{\frac{- h_{2}}{h_{2}} = {- 1}} & \lbrack 14\rbrack\end{matrix}$

Comparing equation 13 and equation 14, it is understood that, when aresponse signal is provided from mobile station #1, there are thequadrature component and in-phase component in the synchronous detectionoutput, while, when a response signal is not provided from mobilestation #1, there is no quadrature component but is only the in-phasecomponent in the synchronous detection output. Therefore, the basestation can identify DTX accurately by measuring how distant thesynchronous detection output is from the I axis.

Also, another example case will be described where mobile station #1transmits a response signal using PUCCH #2 (in FIG. 7) and anothermobile station #2 transmits a response signal using PUCCH #1 (in FIG.7). Here, according to the present embodiment, constellation #1 (in FIG.4) is used for the response signal of mobile station #1 andconstellation #2 (in FIG. 21) is used for the response signal of mobilestation #2.

When mobile station #1 and mobile station #2 both transmit a “ACK/ACK”and the base station receives the response signal from mobile station#1, interference given from the response signal of mobile station #2 tothe response signal of mobile station #1 is as follows.

That is, when the “ACK/ACK” and reference signal transmitted from mobilestation #1 are received by the base station via a channel, in the basestation, a response signal represented by (−1−j) h1/√2 and referencesignal represented by (1+j) h1/√2 are found as a correlation output ofmobile station #1.

Also, when the “ACK/ACK” and reference signal transmitted from mobilestation #2 are received by the base station via a channel, in the basestation, a component represented by −h2 is found as interference to theresponse signal of mobile station #1 and a component represented by(1+j) h2/√2 is found as interference to the reference signal of mobilestation #1 in the correlation output of mobile station #1.

Therefore, when the “ACK/ACK” from mobile station #1 and “ACK/ACK” frommobile station #2 are code-multiplexed, in the base station, a responsesignal represented by {−(1+j)h1−√2h2}/√2 and reference signalrepresented by (1+j)(h1+h2)/√2 are found in the correlation output ofmobile station #1. That is, in this case, the output of synchronousdetection in the base station is as shown in equation 15.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 15} \right)\mspace{585mu}} & \; \\{\frac{{{- \left( {1 + j} \right)}h_{1}} - {\sqrt{2}h_{2}}}{\left( {1 + j} \right)\left( {h_{1} + h_{2}} \right)}\;} & \lbrack 15\rbrack\end{matrix}$

Also, when mobile station #2 transmits a “ACK/ACK” and mobile station #1fails to receive control information and does not transmit a responsesignal, in the base station, a response signal represented by −h2 andreference signal represented by (1+j)(h2)/√2 are found in thecorrelation output of mobile station #1. Therefore, in this case, theoutput of synchronous detection in the base station is as shown inequation 16.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 16} \right)\mspace{585mu}} & \; \\{{\frac{{- \sqrt{2}}h_{2}}{\left( {1 + j} \right)h_{2}} = {\frac{- \sqrt{2}}{\left( {1 + j} \right)} = \frac{{- 1} + j}{\sqrt{2}}}}\;} & \lbrack 16\rbrack\end{matrix}$

Comparing equation 15 and equation 16, when a response signal is notprovided from mobile station #1, it is understood that power is providedonly on the axis 45 degrees shifted from the I axis and Q axis (i.e.,45-degree axis). Therefore, the base station can detect DTX accuratelyby measuring how distance the synchronous detection output is from the45-degree axis.

(Embodiment 9)

Similar to Embodiment 7, a case will be described with the presentembodiment where a base station detects that a mobile station fails toreceive control information to carry the resource allocation result ofdownlink data. Here, using the synchronous detection output of areceived signal, the base station decides whether the response signal isan ACK or a NACK, and detects DTX at the same time.

In this case, the identification between ACK, NACK and DTX is performedby a threshold decision using the synchronous detection output. Here, asin Embodiment 1, an example case will be described where mobile station#1 transmits a response signal using PUCCH #1 (in FIG. 7) and mobilestation #2 transmits a response signal using PUCCH #0 (in FIG. 7). Here,the modulation scheme of response signals is BPSK. Therefore,constellation #2 (in FIG. 8) is used for the response signal of mobilestation #1 and constellation #1 (in FIG. 3) is used for the responsesignal of mobile station #2. Also, the signal point of a referencesignal is the same as the signal point of a NACK in FIG. 3, (1/√2,1/√2).

If mobile station #1 that transmits a desired signal is not interferedwith by mobile station #2 at all, the synchronous detection output takesa value close to (1/√2, −1/√2) when the desired signal is a NACK, andthe synchronous detection output takes a value close to (−1/√2, 1/√2)when the desired signal is an ACK. Here, mobile station #1 is influencedby noise, and, consequently, the synchronous detection output does notalways concentrate on one point.

Inter-code interference from mobile station #2 to mobile station #1 willbe described below. The magnitude of power of inter-code interference(i.e., in the power of a signal that is transmitted by mobile station#2, the power that leaks to the correlation output of mobile station #1)is lower than a desired power, and, consequently, as described above,the synchronous detection output takes a value close to (1/√2, −1/√2)when the desired signal is a NACK, and the synchronous detection outputtakes a value close to (−1/√2, 1/√2) when the desired signal is an ACK.

But, when mobile station #1 fails to receive control information tocarry the resource allocation result of downlink data, mobile station #1does not transmit a response signal, and therefore there are only theinterference component from mobile station #2 and noise in thecorrelation output of mobile station #1. In this case, the base stationperforms a synchronous detection of a response signal of mobile station#2 using a reference signal that leaks from mobile station #2, and,consequently, the synchronous detection output takes a value close to(−1/√2, −1/√2) when the response signal of mobile station #2 is an ACK,and the synchronous detection output takes a value close to (1/√2, 1/√2)when the response signal of mobile station #2 is a NACK.

That is, it is understood that, when mobile station #1 transmits aresponse signal, the power of the synchronous detection output of thebase station is high in the line direction of −45 degree sloperepresented by Y=−X, and, when mobile station #1 does not transmit aresponse signal (i.e., in the case of DTX), the power is low in the linedirection of −45 degree slope represented by Y=−X.

FIG. 22 illustrates the probability distribution density of the Q axisamplitude when the synchronous detection output of mobile station #1subject to interference is rotated to the right by 45 degrees on the IQplane. As understood from FIG. 22, if the synchronous detection outputis rotated to the right by 45 degrees, when the desired signal is anACK, the synchronous detection output takes a value close to (0, 1),that is, the Q axis amplitude is close to 1, while, when the desiredsignal is a NACK, the synchronous detection output takes a value closeto (0, −1), that is, the Q axis amplitude is close to −1.

Also, FIG. 23 illustrates the probability distribution density of the Qaxis amplitude when the synchronous detection output of mobile station#1 subject to interference is rotated to the right by 45 degrees on theIQ plane, in a case where the constellation of each response signal isnot rotated on the cyclic shift axis, that is, in a case where, forexample, all mobile stations use the same constellation #2 (in FIG. 8).

In FIG. 22 and FIG. 23, mobile station #1 is interfered with by mobilestations that use other PUCCHs (in FIG. 7) in addition to mobile station#2. Here, the greatest interference is given from mobile station #2 thatuses the ZAC sequence of the adjacent cyclic shift value, to mobilestation #1. Also, in FIG. 22 and FIG. 23, the ACK occurrence rate andthe NACK occurrence rate are equal in all mobile stations, that is, therelationship of ACK:NACK=1:1 holds.

In FIG. 22, α and β represent thresholds for deciding between ACK, NACKand DTX, and, consequently, the base station decides that: mobilestation #1 transmits a NACK if “the Q axis amplitude in the case of thesynchronous detection output rotated to the right by 45 degrees is lessthan α”; mobile station #1 transmits an ACK if “the Q axis amplitude inthe case of the synchronous detection output rotated to the right by 45degrees is greater than β”; and mobile station #1 does not transmit aresponse signal (i.e., DTX) if “the Q axis amplitude in the case of thesynchronous detection output rotated to the right by 45 degrees is equalto or greater than α and equal to or less than β.”

In FIG. 23, when the synchronous detection output in the case of thegreatest interference (i.e., interference from mobile station #2) haspower in the same axis direction as the synchronous detection output ofthe desired signal, and therefore it is difficult to identify betweenACK, NACK and DTX using thresholds α and β. By contrast with this, inFIG. 22, the synchronous detection output in the case of the greatestinterference has power in the axis direction 90 degrees shifted from thesynchronous detection output of the desired signal, and therefore it ispossible to identify between ACK, NACK and DTX using thresholds α and β.

That is, in combination with, for example, the scrambling shown inEmbodiment 1, even when the ACK occurrence rate and NACK occurrence rateare equal, it is possible to improve the accuracy of identifying betweenACK, NACK and DTX in a base station.

Embodiments of the present invention have been described above.

Also, a PUCCH used in the above-described embodiments is a channel tofeed back an ACK or NACK, and therefore may be referred to as an“ACK/NACK channel.”

Also, it is possible to implement the present invention as describedabove, even when other control information than a response signal is fedback.

Also, a mobile station may be referred to as a “UE,” “MT,” “MS” and “STA(station).” Also, a base station may be referred to as a “node B,” “BS”or “AP.” Also, a subcarrier may be referred to as a “tone.” Also, a CPmay be referred to as a “GI (Guard Interval).”

Also, the method of error detection is not limited to CRC.

Also, a method of performing transformation between the frequency domainand the time domain is not limited to IFFT and FFT.

Also, a case has been described with the above-described embodimentswhere the present invention is applied to mobile stations. Here, thepresent invention is also applicable to a fixed radio communicationterminal apparatus in a stationary state and a radio communication relaystation apparatus that performs the same operations with a base stationas a mobile station. That is, the present invention is applicable to allradio communication apparatuses.

Although a case has been described with the above embodiments as anexample where the present invention is implemented with hardware, thepresent invention can be implemented with software.

Furthermore, each function block employed in the description of each ofthe aforementioned embodiments may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC,” “system LSI,” “super LSI,” or“ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSIs, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells in an LSI can be reconfigured is alsopossible.

Further, if integrated circuit technology comes out to replace LSIs as aresult of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosures of Japanese Patent Application No. 2007-280796, filed onOct. 29, 2007, Japanese Patent Application No. 2007-339924, filed onDec. 28, 2007, and Japanese Patent Application No. 2008-268690, filed onOct. 17, 2008, including the specifications, drawings and abstracts, areincorporated herein by reference in their entireties.

Industrial Applicability

The present invention is applicable to, for example, mobilecommunication systems.

The invention claimed is:
 1. A radio communication apparatus comprising:a spreading section configured to multiply an ACK or NACK symbol with anorthogonal sequence, which is one of plural orthogonal sequences, andwith a sequence defined by a cyclic shift value, which is one of pluralcyclic shift values and which is associated with the orthogonalsequence; a scrambling section configured to scramble the ACK or NACKsymbol by 1 or e^(j(π/2)); and a transmitting section configured totransmit the ACK or NACK symbol that is multiplied and scrambled,wherein said scrambling section scrambles the ACK or NACK symbol by 1when a cyclic shift value that defines the sequence, with which the ACKor NACK symbol is multiplied, is one of two cyclic shift values that areassociated with one of the plural orthogonal sequences and that are nextto each other at a set interval, and scrambles the ACK or NACK symbol bye^(j(π/2)) when a cyclic shift value that defines the sequence, withwhich the ACK or NACK symbol is multiplied, is the other of the twocyclic shift values.
 2. The radio communication apparatus according toclaim 1, wherein the set interval is a minimum difference between pluralcyclic shift values that are associated with one of the pluralorthogonal sequences.
 3. The radio communication apparatus according toclaim 1, wherein the set interval is a difference between two cyclicshift values, which are closest to each other among plural cyclic shiftvalues that are associated with one of the plural orthogonal sequences.4. The radio communication apparatus according to claim 1, wherein thecyclic shift value and the orthogonal sequence are determined from anindex of a resource used for transmission of the ACK or NACK symbol, andsaid spreading section multiplies the ACK or NACK symbol with asequence, which is defined by the determined cyclic shift value, andwith the determined orthogonal sequence.
 5. The radio communicationapparatus according to claim 1, wherein plural cyclic shift values, eachof which is incremented by the set interval, are associated with one ofthe plural orthogonal sequences.
 6. The radio communication apparatusaccording to claim 1, wherein: plural cyclic shift values, each of whichis incremented by the set interval, are associated with one of theplural orthogonal sequences; and 1 and e^(j(π/2)) are selectedalternately each time a cyclic shift value that defines the sequence,with which the ACK or NACK symbol is multiplied, is incremented by theset interval, and said scrambling section scrambles the ACK or NACKsymbol by the selected 1 or e^(j(π/2)).
 7. The radio communicationapparatus according to claim 1, wherein: plural first cyclic shiftvalues, which are not next to each other at the set interval, and pluralsecond cyclic shift values, which are not next to each other at the setinterval and which are different from the plural first cyclic shiftvalues, are both associated with one of the plural orthogonal sequences;and said scrambling section scrambles the ACK or NACK symbol by 1 when acyclic shift value that defines the sequence, with which the ACK or NACKsymbol is multiplied, is one of the plural first cyclic shift values,and scrambles the ACK or NACK symbol by e^(j(π/2)) when a cyclic shiftvalue that defines the sequence, with which the ACK or NACK symbol ismultiplied, is one of the plural second cyclic shift values.
 8. Theradio communication apparatus according to claim 1, wherein saidspreading section block-wise spreads the ACK or NACK symbol using theorthogonal sequence.
 9. The radio communication apparatus according toclaim 1, wherein said spreading section multiplies the ACK or NACKsymbol that has been scrambled by 1 or e^(j(π/2)), with the orthogonalsequence and with the sequence defined by the cyclic shift value.
 10. Aradio communication apparatus comprising: a spreading section configuredto multiply an ACK or NACK symbol with an orthogonal sequence, which isone of three orthogonal sequences, and with a sequence defined by acyclic shift value, which is one of twelve cyclic shift values and whichis associated with the orthogonal sequence; a scrambling sectionconfigured to scramble the ACK or NACK symbol by 1 or e^(j(π/2)); and atransmitting section configured to transmit the ACK or NACK symbol thatis multiplied and scrambled, wherein: the twelve cyclic shift values arerepresented by consecutive numbers #0 to #11 in the direction in which acyclic shift value is incremented by a set value; six cyclic shiftvalues represented by #0, #2, #4, #6, #8 and #10 are associated with oneof the three orthogonal sequences; and said scrambling section scramblesthe ACK or NACK symbol by one of 1 and e^(j(π/2)) when a cyclic shiftvalue that defines the sequence, with which the ACK or NACK symbol ismultiplied, is one of cyclic shift values represented by #0, #4, and #8,and scrambles the ACK or NACK symbol by the other of 1 and e^(j(π/2))when a cyclic shift value that defines the sequence, with which the ACKor NACK symbol is multiplied, is one of cyclic shift values representedby #2, #6, and #10.
 11. The radio communication apparatus according toclaim 10, wherein: six cyclic shift values represented by #1, #3, #5,#7, #9 and #11 are associated with one of the other two of the threeorthogonal sequences; and said scrambling section scrambles the ACK orNACK symbol by one of 1 and e^(j(π/2)) when a cyclic shift value thatdefines the sequence, with which the ACK or NACK symbol is multiplied,is one of cyclic shift values represented by #1, #5, and #9, andscrambles the ACK or NACK symbol by the other of 1 and e^(j(π/2)) when acyclic shift value that defines the sequence, with which the ACK or NACKsymbol is multiplied, is one of cyclic shift values represented by #3,#7, and #11.
 12. The radio communication apparatus according to claim10, wherein: six cyclic shift values represented by #1, #3, #5, #7, #9and #11 are associated with one of the other two of the three orthogonalsequences; and said scrambling section scrambles the ACK or NACK symbolby one of 1 and e^(j(π/2)) when a cyclic shift value that defines thesequence, with which the ACK or NACK symbol is multiplied, is one ofcyclic shift values represented by #0, #1, #4, #5, #8 and #9, andscrambles the ACK or NACK symbol by the other of 1 and e^(j(π/2)) when acyclic shift value that defines the sequence, with which the ACK or NACKsymbol is multiplied, is one of cyclic shift values represented by #2,#3, #6, #7, #10 and #11.
 13. A radio communication method comprising:multiplying an ACK or NACK symbol with an orthogonal sequence, which isone of plural orthogonal sequences, and with a sequence defined by acyclic shift value, which is one of plural cyclic shift values and whichis associated with the orthogonal sequence; scrambling the ACK or NACKsymbol by 1 or e^(j(π/2)); and transmitting the ACK or NACK symbol thatis multiplied and scrambled, wherein the ACK or NACK symbol is scrambledby 1 when a cyclic shift value that defines the sequence, with which theACK or NACK symbol is multiplied, is one of two cyclic shift values thatare associated with one of the plural orthogonal sequences and that arenext to each other at a set interval, and is scrambled by e^(j(π/2))when a cyclic shift value that defines the sequence, with which the ACKor NACK symbol is multiplied, is the other of the two cyclic shiftvalues.
 14. The radio communication method according to claim 13,wherein the set interval is a minimum difference between plural cyclicshift values that are associated with one of the plural orthogonalsequences.
 15. The radio communication method according to claim 13,wherein the set interval is a difference between two cyclic shiftvalues, which are closest to each other among plural cyclic shift valuesthat are associated with one of the plural orthogonal sequences.
 16. Theradio communication method according to claim 13, wherein: plural firstcyclic shift values, which are not next to each other at the setinterval, and plural second cyclic shift values, which are not next toeach other at the set interval and which are different from the pluralfirst cyclic shift values, are both associated with one of the pluralorthogonal sequences; and the ACK or NACK symbol is scrambled by 1 whena cyclic shift value that defines the sequence, with which the ACK orNACK symbol is multiplied, is one of the plural first cyclic shiftvalues, and is scrambled by e^(j(π/2)) when a cyclic shift value thatdefines the sequence, with which the ACK or NACK symbol is multiplied,is one of the plural second cyclic shift values.
 17. The radiocommunication method according to claim 13, wherein the ACK or NACKsymbol that has been scrambled by 1 or e^(j(π/2)), is multiplied withthe orthogonal sequence and with the sequence defined by the cyclicshift value.
 18. A radio communication method comprising: multiplying anACK or NACK symbol with an orthogonal sequence, which is one of threeorthogonal sequences, and with a sequence defined by a cyclic shiftvalue, which is one of twelve cyclic shift values and which isassociated with the orthogonal sequence; scrambling the ACK or NACKsymbol by 1 or e^(j(π/2)); and transmitting the ACK or NACK symbol thatis multiplied and scrambled, wherein: the twelve cyclic shift values arerepresented by consecutive numbers #0 to #11 in the direction in which acyclic shift value is incremented by a set value; six cyclic shiftvalues represented by #0, #2, #4, #6, #8 and #10 are associated with oneof the three orthogonal sequences; and the ACK or NACK symbol isscrambled by one of 1 and e^(j(π/2)) when a cyclic shift value thatdefines the sequence, with which the ACK or NACK symbol is multiplied,is one of cyclic shift values represented by #0, #4, and #8, and isscrambled by the other of 1 and e^(j(π/2)) when a cyclic shift valuethat defines the sequence, with which the ACK or NACK symbol ismultiplied, is one of cyclic shift values represented by #2, #6, and#10.
 19. The radio communication method according to claim 18, wherein:six cyclic shift values represented by #1, #3, #5, #7, #9 and #11 areassociated with one of the other two of the three orthogonal sequences;and the ACK or NACK symbol is scrambled by one of 1 and e^(j(π/2)) whena cyclic shift value that defines the sequence, with which the ACK orNACK symbol is multiplied, is one of cyclic shift values represented by#1, #5, and #9, and is scrambled by the other of 1 and e^(j(π/2)) when acyclic shift value that defines the sequence, with which the ACK or NACKsymbol is multiplied, is one of cyclic shift values represented by #3,#7, and #11.
 20. The radio communication method according to claim 18,wherein: six cyclic shift values represented by #1, #3, #5, #7, #9 and#11 are associated with one of the other two of the three orthogonalsequences; and the ACK or NACK symbol is scrambled by one of 1 ande^(j(π/2)) when a cyclic shift value that defines the sequence, withwhich the ACK or NACK symbol is multiplied, is one of cyclic shiftvalues represented by #0, #1, #4, #5, #8 and #9, and is scrambled by theother of 1 and e^(j(π/2)) when a cyclic shift value that defines thesequence, with which the ACK or NACK symbol is multiplied, is one ofcyclic shift values represented by #2, #3, #6, #7, #10 and #11.